Intra Pulse Code Modulation (IPCM) blocks are blocks of uncompressed video or image samples where luma and chroma samples are coded in the coded stream. These blocks are used in the case when the entropy coding unit produces more bits rather than reduces bits when coding the blocks of image samples.
In other words, the pixel values of the IPCM blocks are not compressed, ant thus the raw pixel values of the original image are used. The IPCM block is introduced in the H.264/AVC Video Compression Standard.
When IPCM blocks are coded in a coded stream in the H.264 Video Compression Standard, these IPCM blocks are coded as uncompressed data. No decoding is performed for these blocks. However, post-decoding processing (including filtering such as deblocking filtering) is still performed on the block boundaries which tend to be a cause of deterioration in image quality (for example, see Non-patent Literature (NPL) 1).